Michael Chertoff was secretary of homeland security from 2005 to 2009 and is co-founder and executive chairman of the Chertoff Group, a security and risk-management firm.

As alarm mounts over the spread of Ebola, many are concerned that screening travelers who arrive in the United States from West Africa is not sufficiently protective because it will not identify those who carry the virus but are not yet symptomatic. Yet over the past two weeks, the Obama administration and supportive experts saturated the media with the argument that any comprehensive travel restrictions aimed at Ebola-infested regions would be pointless and even counterproductive.

In an unprecedented step, on 17 October federal officials moved to stop studies on three kinds of viruses that alter the pathogens to make them more transmissible or deadly. To buy time for experts to work out a government-wide policy for weighing the risks and benefits of such so-called gain-of-function work, officials are halting all new funding for about two dozen studies and are asking researchers doing ongoing work to agree to a voluntary moratorium. The move took some researchers by surprise because it potentially covers certain studies on any influenza strain—not just two bird strains that are already tightly restricted—as well as two coronaviruses: SARS, which panicked Asia in 2003, and MERS, now spreading from camels to people in the Middle East.